A man believed to have acted as a "handler" in the Mumbai terror attacks that left 166 dead in 2008 has been arrested by Indian police.

Sayed Zabiuddin Ansari is suspected of helping to co-ordinate the atrocities from a base in Pakistan. Detectives think he was the sole Indian among a faction of the Lashkar-e-Taiba (LeT) terrorist group that gave orders to the 10 gunmen from a control room in Karachi.

New Delhi blames the group for the attacks, which stunned India and further damaged fragile relations with its nuclear-armed neighbour Pakistan. The 10 commandos killed commuters, foreigners and wealthy Indian businessmen in the three-day rampage, which included attacks on two luxury hotels, a Jewish centre and a train station.

Ansari is a "vital" part of the deadly conspiracy, according to the Times of India.

Ansari is suspected of tutoring the terrorists in Hindi and using his local knowledge to direct them around Mumbai during the attacks. According to Indian media reports, he told the attackers to tell journalists that the "attack was a trailer and the entire movie was yet to come".

Ansari was reportedly arrested on arrival at Delhi airport on 21 June after being deported from Saudi Arabia at India's request. He is thought to have been travelling on a Pakistani passport under the name Riyasat Ali. Police say he had up to 10 aliases, including Abu Hamza and Abu Jundal.

Detectives say Ansari instructed the gunmen that, if they survived, they were to tell investigators the attacks were revenge for the Indian government's atrocities against Muslims and the plight of Kashmiri Muslims. According to India's Mail Today, he also told the terrorists to claim they were Muslims from Hyderabad's Tolichowki area in an attempt to present the atrocities as homegrown.

Only one of the 10 gunmen emerged from the atrocity alive. There was much confusion over Mohammad Ajmal Kasab's nationality after his arrest, but he turned out to be Pakistani and eventually gave Ansari's name to prosecutors as the terror group's "handler". Kasab was sentenced to death by hanging by a special court in Mumbai in 2010 and is awaiting an execution date.

Meanwhile, India has repeatedly called on Pakistan to take action against Hafiz Saeed, the man blamed for masterminding the Mumbai attacks. In May, the US secretary of state, Hillary Clinton, authorised a $10m reward for information leading to his capture.

Six Americans were killed in the atrocities. The US administration welcomed the arrest. The state department spokeswoman Victoria Nuland told reporters: "We have a strong interest, as we've said since the day of the attack, in the arrest, prosecution and conviction of all those responsible for the 2008 Mumbai attack because our own citizens were among the victims."

Peace talks between India and Pakistan have resumed since the attacks, but New Delhi still suspects Islamabad of dragging its feet in bringing the perpetrators to justice, a charge Pakistan denies.

Last year, the Inter-Services Intelligence Directorate (ISI), Pakistan's premier spy agency, was implicated in the Mumbai plot by David Headley, an American-Pakistani LeT militant who was giving evidence in a trial in the US.

Headley told Indian intelligence services he carried out the surveillance for the Mumbai operation while working for the ISI. His claims were backed up by Kasab, who also told prosecutors during his trial that the attacks were conducted with the support of the ISI.

Ansari is also wanted in connection with other terrorist acts. The Mumbai joint commissioner of police (crime), Himanshu Roy, told local reporters on Monday that Ansari was suspected of involvement in a case from 2006, when a huge haul of arms and explosives was found in a car in Aurangabad, Maharashtra, in western India. He is also wanted for attacks on Mumbai trains in 2006 in which 180 people were killed, the television channel NDTV reported.